Your boiler is continuing to run its internal pump after the heating has switched off to cool down the system, which is a normal operating status rather than a breakdown.

DIY fix possible

Check that at least one radiator valve is fully open to allow water to circulateWait for the pump to stop automatically after the programmed overrun time (usually 5-10 minutes)Ensure the room thermostat is not set right at the current room temperature, causing the boiler to cycle on and off frequently